Grinding wheel



FIG. 1 is a top plan view of a grinding wheel showing our new design;

FIG. 2 is an elevational view, the article being the same throughout in appearance;

FIG. 3 is a bottom plan view; and

FIG. 4 is a cross-sectional view of line 4--4 of FIG. 1 thereof. 

The ornamental design for a grinding wheel, as shown and described. 